other stuff is really none of the government's business

but I found, at census.gov that it is a preliminary test for the 2020 census.

"The Census Bureau is conducting tests in 2015 that could significantly improve the upcoming 2020 Census. There were a number of tests planned, each with different goals and objectives.

The Address Validation Test enabled us to assess the performance of the methods and models that will help us develop the 2020 Census address list and develop workload models. The 2015 Census Test conducted in Maricopa and Savannah allowed us to employ a variety of new methods and advanced technologies that are under consideration for the 2020 Census. The final test in 2015 will be the 2015 National Content Test, and this test will aid us in obtaining a nationwide measure of response rates for Internet and self-response."

I have very mixed feelings about the scope of the census. As a genealogy researcher, I've found the census to be a wealth of information, particularly after 1850 when family members are listed by name and age rather than by age and gender grouping. Later censuses have asked information like rent/own, own a radio, type of work and industry in which the work is done, number of years attending school. However, the year they asked for the number of toilets in the house went way too far. One year, I thought the census was too invasive and I answered with only the number of people in the house eligible to vote (required by law). A census taker came to the house. I asked what will you do when I continue to refuse to answer. The answer: they will get the information from the neighbors. Now, as a genealogist, this is unsettling as we now have to figure whether the individual gave the information or whether a neighbor did which could make it unreliable.

So, since the 2015 seems to be a test, you might let them know which questions you find violate your right to privacy and which ones you think are responsive to your legal obligation to furnish information. Might make a difference when the 2020 comes out.

By the way, the most current census return available is the 1940, for anyone wanting to look at it.